1. Field of the Invention
The present invention relates to a photographing apparatus, a photographing controller, a photographing control method, and a photographing control program.
2. Description of Related Art
In the related art, photographing apparatuses configured to photograph (capture) a plurality of images for use in image synthesis have been proposed. For example, in an image-inputting apparatus (i.e., a photographing apparatus, such as a digital camera) disclosed in Japanese Unexamined Patent Publication No. H08-265522, a plurality of images are photographed, for use in image synthesis, by capturing images while shifting the position of the optical axis relative to the image sensor in the horizontal and vertical directions. Specifically, image signals for four images, i.e., an image at the origin, an image horizontally shifted by a ½ pixel, an image vertically shifted by a ½ pixel, and an image that is both horizontally and vertical by a ½ pixel, which are shifted by a lens controller via an optical-axis shift controller, are stored in a memory, in that order. Thereafter, upon the storing of the image signals for the four images into the memory being completed, a lens unit returns to the origin in accordance with a control of the lens controller. Subsequently, the image signal at the origin position is sent back to an arithmetic circuit. The arithmetic circuit, carries out a difference evaluation between the image signal at the reentered origin and the image signal at the origin stored in the memory in accordance with a predetermined evaluation function, the evaluation result is output to an invalidation determination circuit. The invalidation determination circuit, compares the sun of the absolute values that constitute the entered evaluation result with a predetermined threshold value; if the sum of the absolute values is greater than the predetermined threshold value, the high-resolution still image signals, configured of the stored image signals of the four images, are determined as invalid, and the main controller is alerted accordingly. Upon the main controller receiving an alert that the high-resolution still image signals are invalid from the invalidation determination circuit, the main controller externally alerts that the stored high-resolution still images are invalid, and a control operation for reentering the high-resolution still images is carried out.
However, in the image-inputting apparatus of the above-mentioned Japanese Unexamined Patent Publication No. H08-265522, since the invalidation determination is carried out by using the image at the origin when the lens unit is initially positioned at the origin and the image at the origin when the lens unit has returned to the origin upon shifting per pixel unit, in the case where the invalidation determination circuit determines that the high-resolution still image signals are “invalid”, five images are photographed again. Namely, since a “retry process” is performed as one set of “five photographed images”, there is a possibility of an undesirably increased number of photographs being required until a high-resolution synthesized image can be obtained. Therefore, the amount of calculations performed in the image-inputting apparatus increases, and a photographic opportunity may be missed.
Furthermore, if the “photographing conditions” in the images (i.e., pixel-shifted images) other than those at the origin change (due to, e.g., an object being photographed moving, vibration being applied to the camera, an obstacle occurring, or a change in the light intensity (flickering), etc.), the image-inputting apparatus of the above-mentioned. Japanese Unexamined Patent Publication No. H08-265522 does not determine the high-resolution still image signals as “invalid” (the determination does not take into consideration whether the change in the photographing conditions is “invalid”), thereby resulting in the possibility of the image quality of the synthesized image being deteriorated.